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In the 1890s, Edward H. Angles proposed a classification system for malocclusion, which revolutionized the field of orthodontics. He suggested that as long as the top and bottom molars were arranged in a smoothly curving line of occlusion and connected so that the mesiobuccal cusp of the upper molar occluded in the buccal groove of the lower molar, then normal occlusion would result. Concurrently, this comprehensive system provided clarity and simplicity to defining healthy dentition alignment with its categorization of major types of malocclusion. Angle delineated three distinct forms of malocclusion, as determined by the occlusal relationship of the first molars: Class I: An incorrect line of occlusion due to misaligned teeth, rotations or other issues Class II: A distal positioning of the lower molar against its upper equivalent, with no reference to line of occlusion given Class III: The lower molar being mesial to its counterpart, again without a noted line of occlusion.[5] The Angle classification divides occlusion and malocclusion into four distinct classes: normal occlusion, Class I, II, and III. Although both normal occlusion and Class I have the same molar alignment relationship, there is a distinction in how their teeth are organized in relation to the line of occlusion. As for Classes II and III malocclusion, it depends whether or not the line of occlusion is accurate. Once a molar position is determined, a line of occlusion forms along its central fossa that smoothly meanders across both upper and lower teeth. This line follows through on all canine and incisor cingulums as well as down along buccal cusps and incisal edges of lower teeth. All this establishes both interarch and occlusal relationships.[5]